It's NCR owned farmland. It produces a lot of the crops that supply McCarran and the Dam. The farmers are all civilians, though. They work the farms, and in return they get a safe place to stay and clean food and water. Some of 'em aren't all that grateful, though.
Dozens of plants including Maize and Honey mesquite pods are within the greenhouses for the player's pickings. No Karma loss or NCR reputation penalties will be incurred despite the plants marked as owned.